Assessment of Capacitor-based Charge Estimators for Piezoelectric Actuators

This paper focuses at charge estimators of piezoelectric actuators with a sensing capacitor. They have been claimed in the literature to be outperformed by their newly emerged competitors, charge estimators with a sensing resistor, widely known as digital charge estimators. This paper proposes a digital implementation of capacitor-based estimators and compares them with resistor-based ones both analytically and experimentally. Although, the sensing capacitors are normally bulkier than the sensing resistors used in newer resistor-based estimators; a resistor-based estimator needs to have a variable resistance to deal with different excitation frequencies satisfactorily; this is a major drawback which does not exist in capacitor-based estimators. Both capacitor-based and resistor-based estimators, if designed appropriately, are quite comparable in terms of voltage drop and range of measurable charge. This research concludes that capacitor-based estimators, with right design and implementation, can be still of wide use in nanopositioning.